This Nonprovisional application claims priority under 35 U.S.C. xc2xa7 119(a) on Patent Application No(s). 092122853 filed in Taiwan on Aug. 20, 2003, the entire contents of which are hereby incorporated by reference.
1. Field of Invention
The invention relates to a manufacturing method of transistors and, in particular, to a manufacturing method of carbon nanotube transistors.
2. Related Art
In the trend of miniaturization, the manufacturing processes of the integrated circuit (IC) based upon silicon wafers are facing bottleneck problems in optics and physics and pressures from research investments. People have started trying various kinds of nanotransistors made from nanomolecules, so that hundreds of times more transistors than the prior art can be put into a same area. A nanometer is one-billionth meter. In the development of all sorts of nanotransistors, the technique that uses carbon nanotubes as the basic building blocks is the fastest. It is expected to be the best material for nano-grade computer products in the next generation.
The carbon nanotube was discovered by Japan NEC researcher in 1991 when he was studying carbon family chemicals. It is a cylindrical carbon material with a diameter between 1 and 30 nanometers. The carbon nanotube is known to be the thinnest tube discovered in Nature. It is thermally conductive, electrically conductive, robust, chemically stable, and soft. It is mainly comprised of one or several layers of unsaturated graphene layer. These little tubes are actually elliptical micro molecules. They are formed under high temperatures in the water vapor generated by carbon arc and laser. The central portion of the carbon nanotube graphene layer completely consists of six-cite rings. Both ends of the turning points have five- or seven-cite rings. Each carbon atom has the SP2 structure. Basically, the structure and chemical properties of the graphene layer on the carbon nanotube are similar to carbon sixty (C60). The carbon nanotubes can be semiconductors or conductors. Because of this special property, the carbon nanotube plays an important role in electronic circuits.
A necessary condition for using carbon nanotubes in future circuits is that they can be used to make transistors. The semiconductor carbon nanotube can be used as the gate in a field effect transistor (FET). Imposing a voltage can increase its conductivity to be 106 times that of the silicon semiconductor. The operating frequency can reach 1012 Hz, which is 1000 times the frequency that can reached by current CMOS. IBM has successfully used individual single wall or multi wall carbon nanotube as the channel of FET""s to obtain carbon nanotube transistors for test. The single wall carbon nanotubes (SWNT""s) consist of a single shell of carbon atoms. The so-called CNT is a macro carbon molecule with many properties. There are single wall CNT (SWCNT) and multiple wall CNT (MWCNT). There are three kinds of carbon nanotube preparation methods. The first is called the plasma discharging method; the second is called the laser ablation method; and the third is called the metal catalyst thermal chemical vapor deposition method, in which the carbon nanotubes are formed by using iron, cobalt, and nickel metal particles to thermally decompose acetylene or methane in a high-temperature furnace.
Using the reactions in the third type carbon nanotube production method, the disclosed manufacturing method of carbon nanotube FET""s does not require the use of highly pollutant alkaline metals. The processes involved are very simple and compatible with existing IC processes.
An objective of the invention is to provide a manufacturing method of carbon nanotube transistors to solve the foregoing problems and difficulties in the prior art.
Another objective of the invention is to provide a manufacturing method of carbon nanotube transistors to simplify the conventional production processes. With currently available equipment, the production and research costs can be greatly reduced.
We disclose a general embodiment to demonstrate the invention can achieve the above objectives. The detailed steps include: forming an insulating layer on a substrate; forming a first oxide layer on the insulating layer using a solution with cobalt ion catalyst by spin-on-glass (SOG); forming a second oxide layer on the first oxide layer using a solution without the catalyst; forming a blind hole on the second oxide layer using photolithographic and etching processes, the blind hole exposing the first oxide layer, the sidewall of the second oxide layer, and the insulating layer; forming a single wall carbon nanotube (SWNT) connecting the first oxide layer separated by the blind hole and parallel to the substrate; and forming a source and a drain connecting to both ends of the SWNT, respectively.